Meromixis in an antarctic fjord: a precursor to meromictic lakes on an isostatically rising coastline

Abstract

Physico-chemical data and isotopic studies (utilising H14C0,, H2180, 3H20) suggest that hypersaline meromixis in Ellis Fjord (Vestfold Hills, Antarctica) was initiated during the middle Holocene period, when hypersaline brine, excluded during the annual formation of sea-ice, gravitated in a density current to the bottom. The application of this contemporary information to the genesis of the meromictic lakes found today in the Vestfold Hills, suggest that their meromixis may have developed prior to isolation from the sea. Comparison of physico-chemical data from the meromictic basins of Ellis Fjord with that of the Vestfold Hills saline lake allows some determination of their evolutionary pathways initiated before, during and after isolation from the sea. Further evolution of each lake can be explained through the individual interaction between climate, the catchment size and basin morphology.

The chemical development of a hypersaline coastal basin in the High Arctic

“…4): (1) 01 October-01 February: Stable salinity signifies that rejected brine has not penetrated to a depth of 3.3 m in the middle of the basin. Most rejected brine is contained within a layer of water adjacent to the ice surface, which increases in density and thickness as ice growth continues (Gallagher et al 1989). Additionally, some downward migration of brine may take place at the basin edges (Welch 1991), which is not apparent in the central sampling location.…”

“…The internal tide amplitude is less than 20 cm (Fig. 7), likely dampened by sill geometry that reduces mechanical energy input (Gallagher et al 1989). The distinct isotopic signature of the lower water column from standard marine waters indicates that there is currently little mixing of marine waters below the chemocline.…”

“…If evaporation or ablation is high, water bodies will become hypersaline, as salts are concentrated. Alternatively, if freshwater inputs are high, the influx of freshwater will eventually flush relict saltwater from the basin (Gallagher et al 1989;Van Hove et al 2006). Although the former has been suggested to explain the salinity of some Antarctic lakes (Burton 1981), in the Arctic, evaporative enrichment is minor during the short summer season, and ice ablation rates are low because of snow cover for at least 8 months of the year.…”

“…In the Arctic Ocean, as in lakes, hypersaline waters can develop from brine rejection during sea-ice formation (Matthews and Stringer 1984). In less dynamic and deeper settings, density currents formed by brine may concentrate and trap brines at depth, even in marine basins (Gallagher et al 1989). Hypersalinity in marine waters before isolation may be an important precursor to meromictic lakes (Burton 1981).…”

“…1). The basin is referred to as a lake, as water exchange with the ocean is absent for more than 6 months of the year (Gallagher et al 1989). The basin is at sea level, and has an approximately 1-m-deep outlet (July 2008) that facilitates tidal interaction during the summer (Fig.…”